kconfig check: apparmor and iwd

Add several commits to implement pmbootstrap kconfig check for apparmor and iwd.

Note regarding the value for CONFIG_LSM: this is what Alpine uses in aports.git plus apparmor at the end.

See the individual commits for details:

pmb.parse.kconfig.check: git friendly arguments

Put each component argument into a separate line, as these get changed
whenever adding a new kernel config check. I'm about to add two new
ones.

kconfig check: support strings too

Extend the kconfig check code to not only support booleans and arrays,
but also strings. This will be used for CONFIG_LSM with apparmor where
it's important that "apparmor" has a certain spot in the list.

pmbootstrap kconfig check: add apparmor check

SECURITY_APPARMOR_BOOTPARAM_VALUE was required to enable it by default
until 5.1 where the option was removed:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0102fb83f90050b86ce37aec810ea17bb4448e0c

pmb.config.necessary_kconfig_*: tweak comments

Improve the comments for consistency and to give a little more info than
just repeating the variable name.

pmbootstrap kconfig check: add iwd check

iwd seems like a promising alternative to wpa_supplicant. It uses crypto
implementations from the kernel, so let's make kconfig check aware of
the options it needs.

Related: #1864 (closed)